The malignant skin tumor that forms "pearly papules" on sun-exposed skin is basal cell carcinoma. A characteristic feature of this tumor is palisading of the basal cell-like nuclei at the edge of clusters of cells penetrating into the dermis. Basal cell carcinomas almost never metastasize, but can be very locally destructive, and resection of large ones on the face may produce disfiguring scars. Viral cytoplasmic inclusions are a feature of the infectious lesion molluscum contagiosum. Keratin pearls are a feature of squamous cell carcinoma. Melanin and S-100 positivity with immunohistochemical stains are features of melanoma Ref: Robbins Basic Pathology, 8th Ed, page 852-855